code: def is_dask_backend(
      backend: Optional["Backend"],
  ) -> bool:  # noqa: F821
      """Returns whether the backend's dataframe is dask."""
      return backend is not None and is_dask_lib(
          backend.df_engine.df_lib
      )
  
file_path: ludwig/ludwig/utils/dataframe_utils.py
imports: from typing import Dict, List, Optional, Tuple
  import numpy
  import pandas
  from ludwig.api_annotations import DeveloperAPI
  from ludwig.constants import DASK_MODULE_NAME
  from ludwig.data.dataframe.base import DataFrameEngine
  from ludwig.utils.types import DataFrame
label_desc: Use image node_id 2 for calling a global function with example usage: is_dask_backend(backend) and returns: unknown